Future generation aircraft (including helicopters) now in planning and/or development phases (as well as many present generation aircraft) are complex systems comprised of a large number of interrelated, complex subsystems such as the airframe, powerplant, flight controls, avionics, navigation equipment, armament, etc. Such subsystems generate significant amounts of status data, much of which must be frequently monitored by the pilot for the safe and/or efficient operation and/or pilotage of the aircraft. A considerable portion of pilot workload in these future generation aircraft will be devoted to monitoring the status of the aircraft subsystems during flight operations via reference to the generated status data.
In addition, mission requirements for such future generation aircraft may involve a greater percentage of high pilot workload flight operations such as hap-of-the-earth (NOE), adverse weather, and/or night flying. Such high pilot workload flight operations require the pilot to maintain a continual spatial awareness of aircraft orientation and/or location with respect to the external world and a situational awareness of objects of interest in the external world vis-a-vis the aircraft in addition to continual monitoring of the status of aircraft subsystems.
It will be appreciated that the task of monitoring the status of the various aircraft subsystems may conflict with the tasks of maintaining continual spatial and situational awareness of the external world. To monitor the status of aircraft subsystems, the pilot may have to divert his attention from the observation of the external world outside the cockpit to reference generated status data. Such diversions may lead to losses, in varying degrees, of spatial and/or situational awareness of the external world, which, in turn, may lead to less than optimal flight conditions, especially during high pilot workload flight operations.
Current aircraft design methodology strives to optimize the interrelationship between the functional task of monitoring aircraft status information and the functional tasks of maintaining continual spatial and situational awareness of the external world vis-a-vis the aircraft. Such design methodology seeks systems and methods that allow vital aircraft status information to be accessible to the pilot in such a manner that there is no interference with the continual spatial and situational awareness functions being performed by the pilot. In addition, such aircraft status information should be presented in a manner consonant with the spatial orientation and perspective of the pilot to preclude any decoupling among the various functional tasks. Such decoupling may lead to increased pilot workload (to maintain a viable frame of reference) and/or to pilot disorientation.
Electro-optical systems have been developed to provide aircraft status information to the pilot to facilitate simultaneous accomplishment of both the status monitoring functions and the spatial and situational awareness functions. These systems generate symbolic and digital status information images that correspond to the aircraft status information generated by the various aircraft subsystems and superimpose such symbolic status information images into the pilot's field of vision. The images are typically introduced into the pilot's field of vision by means of collimated light rays so that the symbolic images appear to be at optical infinity with respect to the pilot's visual system.
Thus, the pilot views the external world outside of the cockpit at infinity and simultaneously sees symbolic and digital images at infinity. The superimposition of two sets of images, i.e., the external world and electronically generated symbolic and digital status information images, enable the pilot to simultaneously maintain awareness of the status of the aircraft, the spatial orientation of the aircraft with respect to the external world, and a situational awareness of the external world vis-a-vis the aircraft.
Exemplary prior art electro-optical systems utilizing collimated light rays to generate symbolic images include head-up display (HUD) subsystems and helmet mounted display (HMD) subsystems. Representative examples of HUD and HMD subsystems are illustrated in U.S. Pat. Nos. 4,446,480, 4,439,775, 4,439,157, 4,305,057, 4,269,476, and 3,923,370. While such electro-optical systems have contributed significantly to the optimization of the interrelationship between the functional task of monitoring aircraft status information and the functional tasks of maintaining continual spatial and situational awareness of the external world vis-a-vis the aircraft during both visual and non-visual flight conditions, a problem has been identified that interferes with the functional tasks of maintaining spatial and situational awareness of the external world vis-a-vis the aircraft.
During visual flight conditions, the pilot utilizes a cognitive mechanism that allows the pilot to safely and efficiently maintain continual spatial and situational awareness of the external world vis-a-vis the aircraft. More specifically, the pilot, either consciously or subliminally, utilizes the canopy structure of the aircraft as a frame of reference to orientate his visual view of the external world vis-a-vis the aircraft. This cognitive mechanism precludes pilot disorientation during visual flight conditions inasmuch as the canopy structure provides an effective reference for maintaining spatial and situational awareness of the external world. A useful analogy would be the automobile driver who utilizes the hood and front bumpers of his automobile to maintain a continual spatial and situational awareness of the external world, i.e., the relationship of his automobile to the road, other traffic, pedestrians, etc.
During non-visual flight conditions such as night and/or adverse weather flight operations, a pilot cannot generally rely on the cognitive mechanism described in the preceding paragraphs. Many times the non-visual flight conditions are such that the pilot cannot visually perceive the canopy structure and/or the external world, and therefore cannot effectuate a referential relationship between the canopy structure and the external world to facilitate maintenance of spatial and situational awareness of the external world. Moreover, to an increasing degree, pilots operating an aircraft in non-visual flight conditions utilize virtual images of the external world, which are coupled into the pilot's field of view by means of the aforedescribed electro-optical systems, for pilotage of the aircraft.
Such virtual images may be generated by various sensor systems such as low-light television systems, infrared imaging systems, etc. A common characteristic of such virtual image generating systems is that the frame of reference of such generated virtual images of the external world is totally divorced from the canopy structure. For example, a virtual image generating system is typically located in the nose section or the forward belly section of an aircraft so as to generate virtual images of the aircraft's projected flight path. Such virtual images, especially where the aircraft is engaging in flight maneuvers other than straight and level flight, cannot be easily correlated to the canopy structure of the aircraft, which provides an essential underpinning for the utilization of the aforedescribed cognitive mechanism during flight operations.
As a result, pilots utilizing virtual images to pilot aircraft in non-visual flight conditions may become easily disorientated when engaging in flight maneuvers other than straight and level flight. Such disorientation adversely affects the safe pilotage of the aircraft, especially in high pilot workload flight conditions such as NOE flight operations. A need exists to provide pilots utilizing virtual images for non-visual flight conditions with an aircraft referent that will allow the pilot to utilize the cognitive mechanism that the pilot utilizes during visual flight conditions to maintain continual spatial and situational awareness of the external world vis-a-vis the aircraft during flight operations utilizing virtual images of the external world.